Design Of Signal Processing Circuit Based On The Plasma Position Measurement

Electromagnetic diagnostic system is mainly used for the measurement of the plasmamacro parameters, the discharge experiment and plasma control in tokomaks.Electromagnetic diagnostic system includes the measurement of the plasma current, plasmadisplacement, each magnetic field current, these diagnostic systems are made up ofdifferent forms of magnetic coils. This paper applied hardware analog circuit, combinedwith signal processing methods, designed the signal processing circuit based on the positionmeasurement.The design are made up of hardware analog circuits, the subsequent processing of thesignal measured by the position magnetic coils, including previous level signal integrationprocessing, follow-up on the output signal or feedback signal synthesis operation. Usually,the circuit works at short range temperatures, and short time, in order to achieve theadjustment of the operation of the circuit, we used special control circuit which is triggeredby5V TTL(Transistor-Transistor Logic) level and has less than5ms time delay. In analogintegrator, we used static offset compensation method to eliminate the impact by the offsetinput voltage, current and the bias current, at the same time, the low temperature driftcomponents and the operational amplifier has been used, the integration time constant is10ms,output drift is less than10mV/1s. In signal operational circuit part, there are threeinput signal channels and single output signal channel; the signal operational coefficientsare setting conveniently. In this circuit, input signal voltage range for-5V~+5V, outputvoltage range for-10V~+10V, output impedance is50Ω.The functions of the designed circuit were simulated and tested, also verified in thedischarge experiment. The specific implementation process include the following sections,used software to simulate the functions of the circuit for the practical feasibility of thecircuit, tested whether the parameters of the circuit board meet the design requirements ornot through platform experiment, verified the logical function of all circuit module levels,at last detected the actual work of the circuit in the discharge experiment, confirmed thepractical feasibility of the circuit. The results of the discharge experiment show that theoutput signal of this circuit meets the requirement of experiment, also has high signal noiseratio (SNR).